Effect of Dissolved Oxygen on Biological Phosphorous Removal in Continuous-Flow Anoxic-Oxic Process Using Starch as Sole Carbon Source

Abstract

Previous research has demonstrated that biological phosphorus removal (BPR) could be induced by an anoxic-aerobic sequencing batch reactor (SBR). This study applies a continuous-flow anoxic-oxic (AO) reactor at laboratory scale. Synthetic wastewater is used as feed water, in which soluble starch is the sole organic substance added as a carbon source. Effects of dissolved oxygen (DO) concentration on the BPR in the continuous-flow AO process are investigated. Results show that P removal is achieved mainly by denitrifying phosphate-accumulating organisms (DPAOs) without a specific anaerobic period in the system. Glycogen is the main energy source for phosphorous removal in this study, which is different from that of traditional biological phosphorous removal. The DO concentration in the aerobic unit affects anoxic P removal efficiency. Phosphorus removal efficiency as high as 82% is achieved at a lower DO level (.5 mg/L) due to the presence of more nitrate as an electron acceptor for P uptake. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis proves that the microbial community structure changes significantly due to the change of the DO level. Acidobacterium and Proteobacterium play dominant roles in BPR. This study confirms that bacteria using starch can achieve high N and P removal efficiency, and a controlled concentration of dissolved oxygen is of benefit to the BNR of the continuous-flow AO system.